Bipolar transistors are known. Field Effect Transistors (FETs) are known. It is desirable to make each of these types of semiconductor devices as small as possible without losing either the device's current carrying capabilities or the current/voltage gain that is characteristic to each device type. FET current (I.sub.d) is proportional to device width (W), so to increase current, FET's are widened. Unfortunately, device capacitances and especially gate capacitance (C.sub.g) is also proportional to W. Consequently, increasing prior art FET current capacity also meant accepting larger gate capacitance and as a result, larger loads. It also meant device area grew instead of shrunk.
Optically switched transistors are also known. An Opto-isolator, for example, is, basically, a Light Emitting Diode (LED) in close proximity to an optically switched transistor. The LED emits light that turns on the optically switched transistor, switching it from off to on. Optical receivers provide a significant performance advantage over typical voltage signal receivers. Optical receivers also provide a simple solution to the problems associated with interfacing to long-distance optical transmission signals, and to incompatible logic families and signal levels. The performance advantage results because optical signals, generally, do not suffer from the transmission line effects (overshoot, undershoot, ringing, etc.) normally associated with electrical signals. Ringing on a signal forces the receiver to have built-in insensitivity to ringing or to wait until ringing subsides sufficiently. Either way, ringing delays signal recognition. A delay that is avoided with an optically switched receiver.
Similar to the overshoot and undershoot problem is that of interfacing incompatible logic families/signals, e.g., interfacing a low voltage CMOS receiver (with 2.5-3.5 V power supply levels) to a telephone line with potential voltage swings in excess of 20 V. Direct connection could destroy the CMOS receiver circuit. So, an appreciable amount of interface circuitry is required to connect these two incompatible circuits. Unfortunately, it has not been possible to imbed optical receivers into silicon integrated circuit chips.
Prior art optical transistors have been implemented in Group III-V semiconductor technology, primarily in GaAs, but not in Group IV semiconductor materials, and in particular, not in silicon based technology. See, for example, "Quantum Dots of Ge Embedded in SiO.sub.2 Thin Films: Optical Properties," by M. Fugii, S. Hayashi and K. Yamamoto, 20th International Conference on the Physics of Semiconductors, Vol. 3, pp. 2375-2378 (1990) which discusses luminescence from microcrystallites of Ge embedded in SiO.sub.2, indicating the existence of zero dimensional quantum dots. However, these dots are not connected electrically and are, therefore, not usable for devices.
Quantum wires are known for Group III-V materials and used for fabricating semiconductor lasers, See, for example, U.S. Pat. No. 4,748,132 "Micro Fabrication Process for Semiconductor Structure using Coherent Electron Beams," to Fukuzawa et al., incorporated herein by reference. Quantum wires are semiconductor wires so thin as to enable exploitation of the quantum size effect on carriers.